Spectra of prompt electrons from decays of B+ and B0 mesons and ratio of inclusive semielectronic branching fractions

We present spectra of prompt electrons from decays of neutral and charged B mesons. The results are based on 140 /fb of data collected by the Belle detector on the Upsilon(4S) resonance at the KEKB e+e- asymmetric collider. We tag Upsilon(4S) -> B \bar{B} events by reconstructing a B meson in one of several hadronic decay modes; the semileptonic decay of the other B meson is inferred from the presence of an identified electron. We obtain for charged and neutral B mesons the partial rates of semileptonic decay, to electrons with momentum greater than 0.6 GeV/c in the B rest frame, and their ratio b_+/b_0 = 1.08 +- 0.05 +- 0.02, where the first and second errors are statistical and systematic, respectively.Comment: 16 pages, 2 figure files, submitted to Phys. Lett.

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

The first observation of τ±→ϕK±ν\tau^{\pm} \to \phi K^{\pm} \nu decay

We present the first measurement of tau-decays to hadronic final states with a $\phi$-meson. This is based on 401.4 fb$^{-1}$ of data accumulated at the Belle experiment. The branching ratio obtained is $B(\tau^{\pm}\to\phi K^{\pm}\nu) = (4.06\pm 0.25\pm 0.26)\times 10^{-5}$.Comment: 10 pages, 5 figures, ICHEP2006 contribution pape

Search for Lepton Flavor Violating tau- Decays Including with a K0s Meson

We have searched for the lepton flavor violating decays \tau^-\to \ell^-\ks ($\ell = e {or} \mu$), using a data sample of 281 fb$^{-1}$ collected with the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. No evidence for a signal was found in either of the decay modes, and we set the following upper limits for the branching fractions: {\cal{B}}(\tau^-\to e^-\ks) < 5.6\times 10^{-8} and {\cal{B}}(\tau^-\to \mu^-\ks) < 4.9\times 10^{-8} at the 90% confidence level. These results improve the previously published limits set by the CLEO collaboration by factors of 16 and 19, respectively.Comment: 9 pages, 3figures, submitted to Phys.Lett.

Search for the decay B0 to gamma gamma

The rare decay B0 -> gamma gamma is searched for in 104 fb^-1 of data, corresponding to 111 x 10^6 BBar pairs, collected with the Belle detector at the KEKB asymmetric-energy e+ e- collider. No evidence for the signal is found, and an upper limit of 6.2 x 10^-7 at 90% confidence level is set for the corresponding branching fraction.Comment: 7 pages, 3 figures, accepted for publication by Phys. Rev.

Measurement of Branching Fractions for B→χc1(2)K(K∗)B\to {\chi}_{c1(2)} K (K^*) at Belle

We have measured the branching fractions for the exclusive decay modes $B\to {\chi}_{c1(2)} K(K^*)$ using a $140~{\rm fb}^{-1}$ data sample collected by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The measured branching fractions for $B^+\to {\chi}_{c1}K^+$, $B^0\to {\chi}_{c1}K^0$, $B^0\to {\chi}_{c1}K^{*0}$ and $B^+\to {\chi}_{c1}K^{*+}$ decay modes are $(4.5\pm 0.2\pm0.5)\times 10^{-4}$, $(3.5\pm 0.3\pm0.5)\times 10^{-4}$, $(3.1\pm 0.3\pm0.7)\times 10^{-4}$ and $(4.1\pm 0.6\pm0.9)\times 10^{-4}$, respectively, where the first error is statistical and the second error is systematic. We do not observe statistically significant signals for the $B\to {\chi}_{c2}K(K^*)$ decay modes and set upper limits at the 90% confidence level. We also study the helicity distribution for $B\to {\chi}_{c1} K^*$ decay mode and show that the longitudinal polarization component is dominant. {{\it Keywords:} {$B$-meson, Charmonium, Branching Fractions, Polarization}} {{\it PACS:} 13.25.Hw, 11.30.Er}Comment: 21 pages, 5 figures, 3 tables. Submitted to PL

Measurement of gamma gamma -> p p-bar production at Belle

A high precision study of the process gamma gamma -> p p-bar has been performed using a data sample of 89/fb collected with the Belle detector at the KEKB e+e- collider. The cross section of p p-bar production has been measured at two-photon center-of-mass (c.m.) energies between 2.025 and 4.0 GeV and in the c.m. angular range of |cos(theta^*)| eta_c -> p p-bar is observed and the product of the two-photon width of the eta_c and its branching ratio to p p-bar is determined.Comment: 20 pages, 9 figures, Fig.1 added, accepted for publication in Phys. Lett.

Search for lepton flavor violating decays tau- -> l- pi0, l- eta, l- eta'

We have searched for lepton flavor violating semileptonic tau decays using a data sample of 153.8/fb accumulated with the Belle detector at the KEKB e+e- collider. For the six decay modes studied, the observed yield is compatible with the estimated background and the following upper limits are set at the 90% confidence level: B(tau- -> e- eta) mu- eta) < 1.5 x 10^-7, B(tau- -> e- pi0) mu- pi0) < 4.1 x 10^-7, B(tau- -> e- eta') mu- eta') < 4.7 x 10^-7. These results are 10 to 64 times more restrictive than previous limits.Comment: 14 pages, 13 figures, RevTex